It could be Wednesday or later before power is restored to some of the 51,000 Alamance County customers without electricity.

That’s according to Duke Energy’s estimates, released mid-day Saturday. The company has 4,300 people on the ground — including extras from Florida and the Midwest — working to restore power in areas of North Carolina darkened by Friday’s ice storm.

Alamance and Guilford counties were among the hardest hit, with a combined 143,000 customers still without power Saturday. Nearly 80 percent of Duke Energy’s 70,500 Alamance County customers were without electricity Saturday.

“We do know this is going to be a multiple-day outage because of the extent of the damage,” said Duke Energy Communications Manager Tammie McGee. “Our crews are working diligently and won’t stop until the last customer’s power is restored.”

For those without heat and power in the meantime, a Red Cross shelter is open at Graham Recreation Center, at 311 College St., Graham. That shelter can hold more than 200 people. About 47 people stayed there overnight Friday, said Piedmont Carolina Emergency Services Manager Robbie Shatterly.

The Allied Churches of Alamance County’s shelter at 206 N. Fisher St. is also open but was operating on a generator Friday night and Saturday, according to a message from Director Kim Crawford.

Duke Energy’s plan of attack in mass outages like this one is to restore power to essential services, such as hospitals, first, McGee said. Crews then concentrate on areas with the greatest number of customers, eventually working down to areas least affected.

The restoration process includes assessing and prioritizing damage from the largest to the smallest scale. In Alamance County, several of the largest transmission lines were downed in the storm. Those lines provide power from main plants to substations serving neighborhoods. Crews then move to repairing local distribution lines in neighborhoods and commercial areas, down to service lines from poles to individual homes and businesses.

That process will take days to complete in some areas. Limbs, trees and power lines were still coming down at a regular pace Saturday afternoon, with police and fire crews responding.

“We will restore power to the greatest number of customers possible as quickly as possible,” McGee said.